Recently, traffic amount on a network is becoming increasingly larger. Since a bottleneck on the network shifts from a transmission path to a switch device and a router device due to the progress of optical transmission technology, a large capacity switch is required. However, it is a wasteful investment from the economical point of view to introduce a large capacity switch from a stage of small traffic mount.
That is, it is sufficient for a switch to have a small capacity at the initial stage of business. Accordingly, a switch device is required to optionally expand its capacity so that it has a small capacity at first, increases the capacity as the number of users increases, and is finally constructed as a large capacity switch.
There is a multi-stage switch arrangement as one of methods of expanding the switch capacity. The multi-stage switch is disclosed in Patent Document 1.
As shown in FIG. 10, the multi-stage switch disclosed in Patent Document 1 is composed of a plurality of unit switches. For example, a three-stage CLOS switch (CLOS is the name of an inventor) is composed of a three-stage unit switch group including an input stage 8-1, an intermediate stage 8-2, and an output stage 8-3. In the input stage, unit switches 8-11-1 to 8-11-k are arranged by disposing k pieces of m×n unit switches each having m pieces of input lines (FIG. 10 shows only an input line 8-12-1 in input lines 8-12-1 to 8-12-m of a unit switch 8-11-1) and n pieces of output lines (FIG. 10 shows only an output line 8-13-1 in output lines 8-13-1 to 8-12-n of a unit switch 8-11-1) in parallel. In the intermediate stage, unit switches 8-21-1 to 8-21-n are arranged by disposing n pieces of k×h unit switches in parallel. In the output stage, unit switches 8-31-1 to 8-31-h are arranged by disposing h pieces of n×j unit switches in parallel. Note that FIG. 10 shows only an input line 8-32-1 in input lines 8-32-1 to 8-12-n of the unit switch 8-31-1. Further, FIG. 10 shows only an output line 8-33-1 in output lines 8-33-1 to 8-33-j of the unit switch 8-31-1. The unit switch group of the input stage is connected to the unit switch group of the intermediate stage through lines 8-13-1 to 8-13-(n×k), and the unit switch group of the intermediate stage is connected to the unit switch group of the output stage through lines 8-32-1 to 8-32-(n×h), thereby an mk×jh large capacity switch device is arranged.
As described above, in the multi-stage switch arrangement, a switch having a capacity according to the number of unit switches of the respective stages and the number of links corresponding to the number of the unit switches can be arranged by using small capacity unit switches.
Further, there is a stack arrangement as a method of expanding the switch capacity. In the stack arrangement, a plurality of units of the same switch devices are connected and connected to each other so that the switch devices are operated as a large capacity device having ports corresponding to the number of stacks. With this arrangement, the capacity of the device can be expanded to integer times of a unit device.
In contrast, there is a VLAN (Virtual Local Area Network) as a method of using a switch by dividing its capacity. In a port VLAN, a VLAN-ID (Identification) is allocated to each port of a switch so that a VLAN to which a packet to be accepted belongs can be set to the respective ports of the switch. That is, when each VLAN is observed, it seems as if only a part of the switch was divided and used.
Note that Patent Document 2 discloses to subject a switch to logical division as a technology relating to the present invention.
Patent Document 1: Japanese Patent Application Laid-open (JP-A) No. 2002-325087 (FIG. 11 of the Patent Document 1)
Patent Document 2: Japanese Patent Application Laid-open (JP-A) No. 11-232237 (FIG. 14 and paragraph No. (0011) of DESCRIPTION the Patent Document 2).